Hello! This is going to be one of those "title says it all" issues, with the exception that I'll actually include version numbers and a log!

Jokes aside, here they are (I tried to upload the entire file but it was too big for gist's liking):

[06Aug2021 17:46:35.799] [Render thread/ERROR] [cam72cam.mod.ModCore/CATCHING]: Catching cam72cam.mod.serialization.SerializationException: Unable to access field gauge in class class cam72cam.immersiverailroading.items.nbt.RailSettings at cam72cam.mod.serialization.TagSerializer.init(TagSerializer.java:68) ~[universalmodcore:1.1.2] at cam72cam.mod.serialization.TagSerializer.deserialize(TagSerializer.java:145) ~[universalmodcore:1.1.2] at cam72cam.mod.serialization.TagSerializer.deserialize(TagSerializer.java:139) ~[universalmodcore:1.1.2] at cam72cam.immersiverailroading.items.nbt.RailSettings.from(RailSettings.java:78) ~[immersiverailroading:1.16.5-forge-1.9.0] at cam72cam.immersiverailroading.util.RailInfo.<init>(RailInfo.java:98) ~[immersiverailroading:1.16.5-forge-1.9.0] at cam72cam.immersiverailroading.render.item.TrackBlueprintItemModel.render(TrackBlueprintItemModel.java:26) ~[immersiverailroading:1.16.5-forge-1.9.0] at cam72cam.immersiverailroading.render.item.TrackBlueprintItemModel.lambda$getModel$0(TrackBlueprintItemModel.java:23) ~[immersiverailroading:1.16.5-forge-1.9.0] at cam72cam.mod.render.StandardModel.lambda$addCustom$3(StandardModel.java:99) ~[universalmodcore:1.1.2] at cam72cam.mod.render.StandardModel.lambda$renderCustom$5(StandardModel.java:165) ~[universalmodcore:1.1.2] at java.util.ArrayList.forEach(ArrayList.java:1511) ~[?:?] at cam72cam.mod.render.StandardModel.renderCustom(StandardModel.java:165) ~[universalmodcore:1.1.2] at cam72cam.mod.render.StandardModel.render(StandardModel.java:126) ~[universalmodcore:1.1.2] at cam72cam.mod.render.StandardModel.render(StandardModel.java:121) ~[universalmodcore:1.1.2] at cam72cam.mod.render.ItemRender$BakedItemModel.lambda$handlePerspective$0(ItemRender.java:352) ~[universalmodcore:1.1.2] at cam72cam.mod.render.ItemRender$2.func_239207_a_(ItemRender.java:261) ~[universalmodcore:1.1.2] at net.minecraft.client.renderer.ItemRenderer.func_229111_a_(ItemRenderer.java:137) ~[?:?] at com.mrcrayfish.obfuscate.client.Hooks.fireRenderGuiItem(Hooks.java:33) ~[obfuscate:0.6.2-1.16.3] at net.minecraft.client.renderer.ItemRenderer.redirect$bja000$fireRenderGuiItem(ItemRenderer.java:1020) ~[?:?] at net.minecraft.client.renderer.ItemRenderer.func_191962_a(ItemRenderer.java:236) ~[?:?] at net.minecraft.client.renderer.ItemRenderer.func_175042_a(ItemRenderer.java:212) ~[?:?] at com.refinedmods.refinedstorage.screen.BaseScreen.renderItem(BaseScreen.java:298) ~[refinedstorage:1.9.15] at com.refinedmods.refinedstorage.screen.grid.stack.ItemGridStack.draw(ItemGridStack.java:208) ~[refinedstorage:1.9.15] at com.refinedmods.refinedstorage.screen.grid.GridScreen.renderForeground(GridScreen.java:385) ~[refinedstorage:1.9.15] at com.refinedmods.refinedstorage.screen.BaseScreen.func_230451_b_(BaseScreen.java:164) ~[refinedstorage:1.9.15] at net.minecraft.client.gui.screen.inventory.ContainerScreen.func_230430_a_(ContainerScreen.java:122) ~[?:?] at com.refinedmods.refinedstorage.screen.BaseScreen.func_230430_a_(BaseScreen.java:127) ~[refinedstorage:1.9.15] at com.refinedmods.refinedstorage.screen.grid.GridScreen.func_230430_a_(GridScreen.java:356) ~[refinedstorage:1.9.15] at net.minecraftforge.client.ForgeHooksClient.drawScreen(ForgeHooksClient.java:302) ~[forge:?] at net.minecraft.client.renderer.GameRenderer.func_195458_a(GameRenderer.java:492) ~[?:?] at net.minecraft.client.Minecraft.func_195542_b(Minecraft.java:976) ~[?:?] at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:607) ~[?:?] at net.minecraft.client.main.Main.main(Main.java:184) ~[minecraft-1.16.5-client.jar:?] at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:?] at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:78) ~[?:?] at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:?] at java.lang.reflect.Method.invoke(Method.java:567) ~[?:?] at net.minecraftforge.fml.loading.FMLClientLaunchProvider.lambda$launchService$0(FMLClientLaunchProvider.java:51) ~[forge-1.16.5-36.2.2-launcher.jar:36.2] at cpw.mods.modlauncher.LaunchServiceHandlerDecorator.launch(LaunchServiceHandlerDecorator.java:37) [modlauncher-8.0.9.jar:?] at cpw.mods.modlauncher.LaunchServiceHandler.launch(LaunchServiceHandler.java:54) [modlauncher-8.0.9.jar:?] at cpw.mods.modlauncher.LaunchServiceHandler.launch(LaunchServiceHandler.java:72) [modlauncher-8.0.9.jar:?] at cpw.mods.modlauncher.Launcher.run(Launcher.java:82) [modlauncher-8.0.9.jar:?] at cpw.mods.modlauncher.Launcher.main(Launcher.java:66) [modlauncher-8.0.9.jar:?] at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:?] at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:78) ~[?:?] at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:?] at java.lang.reflect.Method.invoke(Method.java:567) ~[?:?] at io.github.zekerzhayard.forgewrapper.installer.Main.main(Main.java:52) [ForgeWrapper-1.5.1.jar:1.5.1] at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:?] at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:78) ~[?:?] at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:?] at java.lang.reflect.Method.invoke(Method.java:567) ~[?:?] at org.multimc.onesix.OneSixLauncher.launchWithMainClass(OneSixLauncher.java:210) [NewLaunch.jar:?] at org.multimc.onesix.OneSixLauncher.launch(OneSixLauncher.java:245) [NewLaunch.jar:?] at org.multimc.EntryPoint.listen(EntryPoint.java:143) [NewLaunch.jar:?] at org.multimc.EntryPoint.main(EntryPoint.java:34) [NewLaunch.jar:?] Caused by: java.lang.NoSuchFieldException: modifiers at java.lang.Class.getDeclaredField(Class.java:2549) ~[?:?] at cam72cam.mod.serialization.TagSerializer.init(TagSerializer.java:64) ~[universalmodcore:1.1.2] ... 54 more

Immersive Railroading Version: 1.16.5-1.9.0
UniversalModCore Version: 1.16.5-1.1.2
Forge Version: 36.2.2

I suspect the issue is in the rendering of the rail item, specifically with some unknown "modifiers", whatever they may be.
Sorry if this is a duplicate issue, I saw some that looked similar but I pretty sure they weren't exactly the same.

Thanks!

Downgrade java to 1.8, I don't yet support newer versions

I figured I should mention that Java 11 seems to work too, as I can hover over the rail item just fine.